Sections of the Anfield crowd booed during the match and at full-time, with the noise particularly sharp when Slot removed Ngumoha in the second half. It later emerged the 17-year-old had told the bench he could no longer continue due to cramp.
Gomez, who came on as a substitute himself when Ibrahima Konaté was replaced during the final quarter, addressed the atmosphere directly speaking to the Liverpool Echo.
"We feel it. It's the last thing we want. For us older boys who have experienced so many good times here, it does hurt. If it didn't then you shouldn't still be here. We want to make it right."
He was clear that the reaction was understandable.
"I understand the frustration, 100%. We've all said on record a few times this year we know this is not where we want to be. The fans pay their hard-earned money to come and watch us and they're entitled to show their frustration, in the same way they cheer us."
Asked whether the boos were aimed specifically at Slot, Gomez declined to be drawn while making the point that results are the only meaningful answer.
"I can't engage or give you a guide on that but, fundamentally, if we win the game there's no boos — so that's the bit we have to do."
On Ngumoha's substitution, Gomez offered the dressing room perspective.
"Rio's young and he played in a high-intensity game. Physically he was tired, and those are the subtle things behind the scenes you probably don't realise. But we get it — Rio is a top player and has the ability to be a bright, bright star for us in the future. But it was the later stages of the game and he's tired. And if he comes off it's like 'oh' — and the fans are entitled to that opinion."
Liverpool need three points from their final two matches to confirm Champions League qualification. They face Aston Villa on Friday before hosting Brentford on the final day. The season has produced 11 Premier League defeats — the most since Brendan Rodgers's final campaign in 2014/15.